Ink-jet printing technology has been developed for many years and in the last two decades ink-jet printing, especially drop-on demand (DOD) ink-jet printing systems have grown to a major topic in scientific research. DOD ink-jet printers are widely used in small businesses and home offices due to their low price, low noise, easiness of full colouration, low space demand, environmental safety, and being able to print various substrates including plain papers, papers for special printing and transparency.
Ink-jet printing is a non-contact method in which droplet of inks are directly projected on to a substrate from very fine nozzles and allowed to adhere to the substrate forming characters and images. The two most popular types of DOD ink-jet printers are thermal and piezoelectric. Compared to conventional manufacturing method ink-jet printing can be carried out in low temperatures. Furthermore, chemical waste can be significantly reduced because ink-jet printers can print only on the desired location without unnecessary post-processing that can damage the actual substrate and material.
Ink-jet printing has become widespread to the point that personal computers readily permit the users to create high grade prints and publishing with various controllable fonts and point sizes, as well as with the ability to print graphics either locally generated or from pre-packaged clip art.
In the past several years, there has been considerable interest in developing computerized, three dimensional printing techniques. Three-dimensional printing is a method of creating three-dimensional objects by depositing or forming thin layers of material in succession so as to build up the desired three dimensional structures. The printers are not however capable of anything other than normal flat printing. Accordingly higher scale stationery, such as business cards and letterhead papers, require raised lettering. Therefore various methods have been devised to create raised letter or image.
In one of the methods, the ink used to provide the wet substrate for the thermo-graphic process, is preferably formulated from the standard inks used in ink-jet printers. Many of the ink-jet printers are designed for operation with water based inks (to prevent clogging) and accordingly a thermo-graphic powder which will adhere thereto is preferably used. The inked paper is then subjected to a dusting with a thermo-graphic powder, formulated to adhere only to the inked portion of the paper, with excess powder being removed from the paper and recycled. Thermo-graphic activation heat (about 132-148° C.) is then used to cause the adhered powder and ink to rise to form the raised text or graphics.
With the current state of thermo-graphy it is not possible to print with alternate sites of raised and non raised lettering and/or graphics in a single pass. Instead two passes are required, one for the flat printing and one for the raised printing, with attendant problems of alignment and proper registrations.
Another technique makes use of a bath of polymerisable liquid material. A thin upper layer of the liquid is cross-linked or hardened in some way, such as electromagnetic radiation (UV, IR), in a pattern which is the same as cross-section through the object to be formed. The electromagnetic radiation spot is moved across the surface in accordance with a digital representation of the relevant cross-section. After one layer is complete the liquid level is raised over a small distance and the process repeated. Each polymerized layer should be sufficiently formed stable to support the next layer.
Another process uses an ink-jet printing technique wherein an ink-jet stream of liquid molten metal or a metal composite material is used to create three-dimensional objects under computer control, similar to the way an ink-jet printer produces two dimensional graphic printing. A metal or metal composite part is produced by ink-jet printing of successive cross sections, one layer after another on a target, using a cold welding (rapid solidification) technique, which causes bonding between the particles and the successive layers.
A second type of printing requiring raised characters is that of Braille printing, which is a representation of alphabetic letters via raised dots (up to six dots/character) in varying configurations. These dots or characters, which are read by finger touch, must be of a minimal standard height for touch sensitive reading by the blind. Currently, the various means for Braille printing are either very labor intensive, or requires expensive machinery and processing. One known method is to use impact printer to emboss paper with raised portions representing the Braille characters. Thus, Braille printing has been affected by using a Braille typewriter which impresses dots on a heavy stock paper or cardboard, such that the dots are raised on the other side of the stock.
Compared with conventional printers, the impact printers can be expensive due to their complexity, noisy due to the constant impacting of the printer and unreliable due to the high forces on the moving parts. Recently, machines have been developed for printing of Braille and other raised lettering and graphics in a thermo-graphic process. These machines, however represent sophisticated technology and are very expensive and accordingly not agreeable for use in common desktop publishing applications. Even with the sophistication of the machines, simultaneous printing of raised and non-raised portions is still not possible, such as the printing of regular text with corresponding clear raised Braille print thereon.
It is therefore an object of the present invention to provide a low cost system for producing raised lettering and graphics in desk top publishing applications. It is a further object of the present invention to produce such raised lettering and graphics by means of a personal computer and an ink-jet type printer.
With appropriate conversion software relative to any language and any Braille language it is possible to simultaneously print the underlying language and the Braille print. A monitor display shows the print field prior to initial printing for desired changes prior to printing. With text scanners being widely and economically available, it is also possible to scan regular typed or printed text and graphics into a computer. With the appropriate conversion software, the scanned text is converted to Braille and is nearly simultaneously printed out in raised Braille print, all without any labor intensive text entry.